1. Field of the Invention
The present invention relates to an apparatus for detecting pulse wave produced from an arterial vessel of a living body.
2. Related Art Statement
The Assignee to which the present application is assigned, previously filed Japanese patent application No. 62-109594 on May 2, 1987 and Japanese Utility Model Application No. 62-178067 on Nov. 20, 1987 in each of which they disclosed a device having a sensor for detecting pulse wave produced from an artery of a subject, the sensor being movable along a cross line crossing the artery so as to be positioned in place relative to the artery, and pressed against a body surface over the artery so as to detect the pulse wave. Each of the devices also has a pair of air-tight chambers formed of bellows or rubber bags, on both sides of the pulse wave sensor, and the pulse wave sensor is moved along the cross line as a result that pressure level in each of the pair of chambers are varied.
The above-indicated pulse wave detecting devices, however, suffer from a problem that, even after the pulse wave sensor has been positioned in place, the sensor may be moved due to changed pressure difference between the pressure levels of the pair of air-tight chambers resulting from, for example, failure of electric power applied to the device or leakage of air from one of the chambers.
The above Japanese patent application No. 62-109594 further teaches that the pulse wave sensor may be moved by means of a feeding screw rotated by a drive motor. This arrangement assures that the sensor is retained in place. However, if the drive motor is located spaced apart from the body surface of the subject via the pulse wave sensor disposed therebetween, an overall height of the pulse wave detecting device would be disadvantageously increased. Japanese patent application No. 62-109594 was laid-open under Publication No. 63-275320 on Nov. 14. 1988.